In the field of measuring the instantaneous flow of an injector for gaseous fuels, it is known to provide a measuring instrument of the type comprising a measuring chamber connected to the injector and further connected to the external environment in a continuous manner through an outlet having a given outlet section; a pressure sensor and a temperature sensor for measuring pressure and temperature of a test gas within the measuring chamber during at least one injection cycle of the injector; and a calculation device for calculating the instantaneous flow of the injector as a function of the measured pressure and temperature values.
The known measuring instruments of the above-described type have some drawbacks, mainly deriving from that the methods of calculating the instantaneous flow in these measuring instruments are relatively inaccurate and complex.